Charged proton enters an electric field

AI Thread Summary
A proton with an initial horizontal velocity enters an upward electric field of 1.0 x 10-7 N/C, leading to confusion about its trajectory. The calculation of net force using the electric force (E x q) and gravitational force (mg) suggests a downward movement, which contradicts the initial horizontal motion. Participants emphasize the importance of precise values for charge and mass in calculations to clarify the forces involved. There is a discussion about whether the forces are close in magnitude, affecting the proton's path. Accurate calculations and a clear understanding of the forces are essential for describing the proton's trajectory correctly.
physicsundergrad123
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Homework Statement
A proton with horizontal velocity enters a region with a constant electric field of 1.0 x 10-7 N/C that points upwards (away from the Earth). Describe the trajectory of the proton
Relevant Equations
(mp=1.67 x 10-27 kg, qp=e=1.6 x 10-19 C).
FE= E x q. Fg= mg
I tried to do Net force with electric field = E x q minus the gravitational force= mg. However, this gives me a negative net force suggesting the proton is moving downwards. I'm not sure this is correct as the initial velocity was horizontal. Was there no gravitational force before? Am I missing a step?
 
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physicsundergrad123 said:
Homework Statement:: A proton with horizontal velocity enters a region with a constant electric field of 1.0 x 10-7 N/C that points upwards (away from the Earth). Describe the trajectory of the proton
Homework Equations:: (mp=1.67 x 10-27 kg, qp=e=1.6 x 10-19 C).
FE= E x q. Fg= mg

Net force with electric field = E x q minus the gravitational force= mg
The force due to the electric field does not involve a vector cross product. The force due to a magnetic field does involve a cross product. Or are you using "x" to represent a multiplication?

If so, can you show your detailed calcs please? Thanks.
 
physicsundergrad123 said:
Homework Statement:: A proton with horizontal velocity enters a region with a constant electric field of 1.0 x 10-7 N/C that points upwards (away from the Earth). Describe the trajectory of the proton
Homework Equations:: (mp=1.67 x 10-27 kg, qp=e=1.6 x 10-19 C).
FE= E x q. Fg= mg

I tried to do Net force with electric field = E x q minus the gravitational force= mg. However, this gives me a negative net force suggesting the proton is moving downwards. I'm not sure this is correct as the initial velocity was horizontal. Was there no gravitational force before? Am I missing a step?
Seems to the the two opposing forces are going to be very close in magnitude, so you will need to use more precise values for charge etc.
Please post your calculation, as requested by @berkeman .
 
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